The present invention relates to a process for manufacture of amorphous metal ribbons in which at least one liquid metal stream is projected onto a receiving surface moving at high speed.
The work carried out since 1958 by Pol Duwez at the California Institute of Technology has led to knowledge of amorphous metal alloys, which are produced by very rapid cooling of a liquid phase, thereby making it possible to preserve the random, or amorphous, structure thereof. Indeed, in this way the temperature of the material is immediately reduced below a certain threshold, called the vitrification temperature, itself located at a temperature much lower than the solidification point at which crystallization begins.
One technique for manufacture of amorphous metal alloys consists of pouring a stream of molten metal onto a surface moving past at high speed, whose temperature is kept below or equal to ambient temperature. In this way, the liquid spreads over the surface in a film having a thickness of only several microns. Because this film is extremely thin and in intimate contact with a heat sink having a much larger volume, and since the metals possess high level of thermal conductivity, the metal cools and solidifies very rapidly, i.e., at a rate of approximately 10.sup.6 .degree.C./second. The surface passing beneath the metal stream may be part of a disk, an endless belt, or a wheel. This surface may incorporate notches perpendicular to its direction of travel, in order to divide the films or ribbons into small segments.
The films or ribbons thus produced possess remarkable mechanical and magnetic properties. Accordingly, the alloys exhibit very high tensile strength, and their ductility is marked by excellent folding strength, thereby making it possible to achieve curvatures around a radius equal to approximately the thickness of the ribbon. They also possess weak magnetism; that is, they are magnetized and demagnetized with a very weak field. Patents Nos. EP-A-59 864, 84 335, and 84 785 are examples from the literature describing processes of this kind.
Industrial-scale production of amorphous metal ribbons poses special problems, since a consistent geometry and quality of the ribbons must be guaranteed over long periods of time.